1. Field of the Invention
This invention relates to a printer for printing a plurality of print data pieces in a predetermined order.
2. Description of the Related Art
Conventional printers normally are used by local connection to data processing systems in a one-to-one correspondence with each other. Thus, generally printers comprise only a single type of connection interface adaptive to the data processing system to be connected to the printer.
However, with change in an information processing environment in recent years, it has been demanded that a printer can cover data processing systems having different types of interfaces. For example, a printer comprising a number of input interfaces such as serial ports and parallel ports, which will be hereinafter called input ports, is provided in response to such a demand.
FIG. 27 shows an example of such a printer having a number of input ports. In the figure, for example, a printer 30 is connected to four data processing systems, hereinafter called hosts, H (H1-H4) via input ports P (P1-P4), and each input port P (P1-P4) is provided with a buffer memory B (B1-B4) having a predetermined capacity.
In the configuration, assume that print commands and data, which will be hereinafter called print jobs, are input to the input ports P from the hosts H at timings as shown in FIG. 28 and are stored in the buffer memories B. At this time, the printer 30 first prints based on the print job input from the host H1 and subsequently prints based on the print jobs input from the hosts H3, H2, and H4 in order. The reason why the conventional printer 30 prints in the above order is that, as shown in FIG. 28, an image formation process is executed in the printer data transfer start order to the input ports P, so that a print request is issued to a print mechanism (not shown), and that at the termination of the print job, an image formation process based on the next received print job is executed.
Thus, the conventional printer 30 starts printing in the print job reception order and does not start printing based on another print job unless the current print job is complete. Therefore, the printer involves the following problem:
In the example shown in FIG. 28, the print jobs sent from the hosts H2-H4 enter a printable state earlier than the print job input from the host H1, but enter a wait state until completion of the print job input from the host H1 because they are late for the print data transfer start time. Thus, an appreciable wait time is contained by the time all print jobs are completed, not only prolonging the total print time in the printer 30, but also making the operator of the host in the wait state irritated.